In recent years, from a perspective of environment protection, many kinds of electrical apparatus are equipped with an inverter circuit for achieving energy conservation and a high efficiency. Especially in an automotive industry, a hybrid electric vehicle (hereinafter, HEV) running with both an electric motor and a combustion engine is introduced into the market. In this circumstance, engineering development for protecting a global environment, saving energy and achieving a high efficiency are being progressed.
A working voltage range of the electric motor for HEV is as high as several hundred. Therefore, a metallized film capacitor having a high withstanding voltage and a low loss characteristics attracts attention as a capacitor to be used for the electric motor. As market requirement for free of maintenance is high, the metallized film capacitor having an extremely long life is being employed in this regard, too.
Among metallized film capacitors, a metallized film capacitor having a metallized electrode formed on a dielectric film has a smaller volume of the electrode than one having a metal foil electrode, so the capacitor is miniaturized and light-weighted. Moreover, the metallized electrode has a unique self-healing characteristic, providing a high reliability against dielectric breakdown. Therefore, the capacitor has been used widely.
As an example of the metallized film, a configuration of conventional metallized film 100 is shown in FIG. 3. FIG. 3 is a cross sectional view of conventional metallized film 100.
Metallized film 100 includes dielectric film 101, metal thin film layer 102 and dielectric layer 104. Metal thin film layer 102 is chiefly made of aluminum deposited on both surfaces of dielectric film 101 by such as a vapor deposition or an ion plating method. Margin 103 is a portion free from metal thin film layer 102. Dielectric layer 104 is formed by applying a dielectric coating to one or both surfaces of dielectric film 10 The coating is formed by dissolving one of polycarbonate, polyphenylene oxide and polyalylate into an organic solvent. Margin 105 is a portion free from dielectric layer 104. After the dielectric coating is applied, the organic solvent contained in the dielectric coating as a diluent is vaporized and dried out, thus metallized film 100 is completed. As the organic solvent, at least one or two of dichloromethane, dichloroethane and trichloroethylene are properly selected for use.
As described, in order to make metallized film 100, a polymer compound to be used for forming dielectric layer 104 is dissolved into an organic solvent and the solution is applied to the dielectric film to form the dielectric layer. For this reason, a heat source and a cooling apparatus for vaporizing and removing the organic solvent are required, or a high performance organic solvent recovering apparatus is required.
PLT 1 proposes to form a dielectric film by using an ultrasonic curing resin as a dielectric coating, therewith forming dielectric film 200 shown in FIG. 4. Namely, metallized film 200 is made as followings. First, metal thin film layer 202 chiefly made of aluminum and margin 203 free from metal thin film layer 202 are formed on both surfaces of dielectric film 201 by such as a vapor deposition method or an ion plating method. Then, the ultraviolet curing coating is applied to at least one surface of dielectric film 201, and then the ultraviolet curing coating is hardened with ultraviolet irradiation, so as to form dielectric layer 204.
The ultraviolet curing coating making up dielectric layer 204 is composed of ultraviolet curing resin added by photopolymerization initiator which promotes curing reaction of the ultraviolet curing resin. That is, the coating does not contain organic solvent, so aforementioned problem related to use of the organic solvent is not caused.